Rain Water Gutter Size

Gutter downspout sizes are 3 to 6 inches.

Rain water gutter size.

But houses with big steep roofs or those located in climates prone to heavy downpours may need wider gutters and extra downspouts to keep rainwater from overflowing. Unless special provisions are made for flexibility in downspouts rain gutters and their support systems gutters should expand away from downspouts and downspouts should not be located near gutter expansion joints. To limit the effects of thermal expansion in gutters 50 ft 15 3 m is a practical maximum length of gutter to be served by a downspout. Then use the chart below to see what size gutter you need.

You should have enough gutter downspouts to effectively handle the size of your entire gutter system. However too large a gutter downspout can look unattractive. 6 inch 7 960 square feet. The gutter and downspout size requirement depends upon the number of sections and length of the gutter sections as well as the number of downspouts.

Adding additional sections of gutter reduces the length of each section and will reduce the gutter size. A square inch of downspout can drain 1 200 square feet of roof during a rain with an intensity of one inch per hour. 5 inch 5 520 square feet. Roof area the locale s rainfall intensity and gutter capacity determine how many square inches of downspout are needed.

Most downspouts are rectangular but they can also be round or square. Doubling the number of downspouts halves the required capacity for each. Five inch k style gutters or 6 inch half rounds the most common residential sizes are able to handle the rainfall on most houses in most parts of the country. See photos below most residential gutters will measure approximately 5 inches across the top with the actual opening being approximately 4 5 inches.

Size downspouts to fit the gutter. Measure your gutter across the top from the back where the gutter meets the home to the outer edge. Use this handy guide to make sure your rain collection is up to the task during even the heaviest storm. If a roof s various drainage areas call for different size gutters go for the biggest one k style.